NAME

SYNOPSIS

DESCRIPTION

VACUUM reclaims storage occupied by dead tuples. In normal PostgreSQL
operation, tuples that are deleted or obsoleted by an update are not
physically removed from their table; they remain present until a VACUUM
is done. Therefore it’s necessary to do VACUUM periodically, especially
on frequently-updated tables.
With no parameter, VACUUM processes every table in the current
database. With a parameter, VACUUM processes only that table.
VACUUMANALYZE performs a VACUUM and then an ANALYZE for each selected
table. This is a handy combination form for routine maintenance
scripts. See ANALYZE [analyze(7)] for more details about its
processing.
Plain VACUUM (without FULL) simply reclaims space and makes it
available for re-use. This form of the command can operate in parallel
with normal reading and writing of the table, as an exclusive lock is
not obtained. VACUUMFULL does more extensive processing, including
moving of tuples across blocks to try to compact the table to the
minimum number of disk blocks. This form is much slower and requires an
exclusive lock on each table while it is being processed.

PARAMETERS

FULL Selects ‘‘full’’ vacuum, which can reclaim more space, but takes
much longer and exclusively locks the table.
FREEZE Selects aggressive ‘‘freezing’’ of tuples. Specifying FREEZE is
equivalent to performing VACUUM with the vacuum_freeze_min_age
parameter set to zero. The FREEZE option is deprecated and will
be removed in a future release; set the parameter instead.
VERBOSE
Prints a detailed vacuum activity report for each table. Can be
used to help determine appropriate settings for max_fsm_pages,
max_fsm_relations, and default_statistics_target.
ANALYZE
Updates statistics used by the planner to determine the most
efficient way to execute a query.
table The name (optionally schema-qualified) of a specific table to
vacuum. Defaults to all tables in the current database.
column The name of a specific column to analyze. Defaults to all
columns.

OUTPUTS

When VERBOSE is specified, VACUUM emits progress messages to indicate
which table is currently being processed. Various statistics about the
tables are printed as well.

NOTES

VACUUM cannot be executed inside a transaction block.
We recommend that active production databases be vacuumed frequently
(at least nightly), in order to remove dead rows. After adding or
deleting a large number of rows, it might be a good idea to issue a
VACUUMANALYZE command for the affected table. This will update the
system catalogs with the results of all recent changes, and allow the
PostgreSQL query planner to make better choices in planning queries.
The FULL option is not recommended for routine use, but might be useful
in special cases. An example is when you have deleted or updated most
of the rows in a table and would like the table to physically shrink to
occupy less disk space and allow faster table scans. VACUUMFULL will
usually shrink the table more than a plain VACUUM would. The FULL
option does not shrink indexes; a periodic REINDEX is still
recommended. In fact, it is often faster to drop all indexes, VACUUMFULL, and recreate the indexes.
VACUUM causes a substantial increase in I/O traffic, which might cause
poor performance for other active sessions. Therefore, it is sometimes
advisable to use the cost-based vacuum delay feature. See in the
documentation for details.
PostgreSQL includes an ‘‘autovacuum’’ facility which can automate
routine vacuum maintenance. For more information about automatic and
manual vacuuming, see in the documentation.